29 November, 2016

The National Institute for Health and Care Excellence (NICE) has published draft guidance proposing that the breast cancer prevention drug Anastrozole be available on the NHS (1).

Research carried out by an international team led by Professor Jack Cuzick of the Queen Mary University of London had previously found that this breast cancer prevention drug reduced the risk of breast cancer in high-risk groups by 53%. (2).

What is Anastrozole, and how does it help prevent breast cancer?

Anastrozole reduces the action of the enzyme aromatase, which converts androgens (male sex hormones) to oestrogen. High levels of oestrogen are associated with an increased risk of breast cancer. Oestrogen encourages a high cell division rate, meaning there is less time for DNA repair and an increased risk for mutations that may lead to cancer. Oestrogen-positive breast cancers require high levels of oestrogen for their growth.

In post-menopausal women, aromatase is mainly found in fatty tissues (such as the breasts), muscle and skin, where most oestrogen is produced.

Anastrozole helps prevent breast cancer in post-menopausal women by blocking the action of aromatase, thereby blocking oestrogen production. It is a prevention treatment for breast cancer following hormone receptor-positive breast cancer diagnosis (3). It is also used as a prevention treatment for women at high risk of developing breast cancer – but this treatment is not currently available on the NHS.

What does high risk mean?

A woman is at ‘high risk’ (4) of breast cancer if she:

  • Has two or more close relatives with breast cancer
  • A mother or sister who developed breast cancer before the age of 50
  • A mother or sister who had breast cancer in both breasts
  • Certain high-risk types of benign breast cancer

Does Anastrozole have any side effects?

The 2014 study by Cuzick et al. (2) indicated that Anastrozole has fewer and less serious side effects than tamoxifen, which is also used as a preventative treatment. However, a more recent study (5) suggests both drugs have a similar number of side effects, though the side effects are different. Women may also develop resistance to Anastrozole (6). Drug resistance means a drug will be less or no longer effective.

Breast Cancer UK’s position

Breast Cancer UK supports preventative medicine and this breast cancer prevention drug, which can be used to help reduce breast cancer in high-risk groups. However, most breast cancers are not in women at high risk. Breast cancer will affect 1 in 8 women at some point in their lifetime (7), and many do not identify as high-risk.

Breast Cancer UK also believes that it is important to question and continue to research why apparently high-risk groups are at higher risk today than they were 50 years ago. A 2003 study (8) found that the risk of getting breast cancer by age 50 for a woman carrying a BRCA mutation who was born before 1940 was 24%, but for those born after 1940 was 67%. This suggests that our lifestyles and modern-day environments could increase our vulnerability to this disease. To truly prevent more breast cancers, we must continue to research and better understand all of the risk factors for breast cancer – including our exposure to potentially harmful chemicals in everyday products such as hormone disrupting chemicals.

All women can reduce their risk of breast cancer by following these top tips

  1. Consume a healthy diet high in fresh fruit and vegetables and, where possible, organically grown.
  2. Reduce or avoid alcohol consumption
  3. Maintain a healthy weight within your recommended BMI
  4. Take plenty of exercise
  5. Reduce your exposure to harmful chemicals.
  6. Breast Cancer UK has called for more research funding into cancer prevention.

The NICE draft guideline update is out for consultation until 29 December 2016.


  1. NICE recommends 4p a day breast cancer drug (https://www.nice.org.uk/news/article/nice-recommends-4p-a-day-breast-cancer-drug) (accessed November 29, 2016)
  2. Cuzick, et al. (2014) Anastrozole for prevention of breast cancer in high-risk postmenopausal women (IBIS-II): an international, double-blind, randomised placebo-controlled trial. The Lancet 383: 1041–1048. https://www.ncbi.nlm.nih.gov/pubmed/24333009
  3. Dowset et al. (2010). Meta-Analysis of Breast Cancer Outcomes in Adjuvant Trials of Aromatase Inhibitors Versus Tamoxifen. Journal of Clinical Oncology 28(3): 509-518. https://www.ncbi.nlm.nih.gov/pubmed/19949017
  4. Cancer Research UK (2013). https://scienceblog.cancerresearchuk.org/2013/12/12/a-new-way-to-prevent-breast-cancer-anastrozole/ (accessed November 29, 2016)
  5. Forbes et al. (2016). Anastrozole versus tamoxifen for the prevention of locoregional and contralateral breast cancer in postmenopausal women with locally excised ductal carcinoma in situ (IBIS-II DCIS): a double-blind, randomised controlled trial. The Lancet 387: 866–873. https://www.ncbi.nlm.nih.gov/pubmed/26686313/
  6. Vilquin et al. (2013). Molecular characterization of anastrozole resistance in breast cancer: Pivotal role of the Akt/mTOR pathway in the emergence of de novo or acquired resistance and importance of combining the allosteric Akt inhibitor MK-2206 with an aromatase inhibitor. International Journal of Cancer Volume 133(7): 1589–1602. https://onlinelibrary.wiley.com/doi/10.1002/ijc.28182/full
  7. Cancer Research UK (2016). https://www.cancerresearchuk.org/health-professional/cancer-statistics/statistics-by-cancer-type/breast-cancer#heading-Zero (accessed November 29, 2016).
  8. King et al. (2003). Breast and ovarian cancer risks due to inherited mutations in BRCA1 and BRCA2. Science 302(5645): 643-646. https://www.ncbi.nlm.nih.gov/pubmed/1457643

Related Articles

15 February 2024

Welcoming our new ambassador – Michelle Ogundehin

Breast Cancer UK (BCUK) is pleased to welcome our new Ambassador, Michelle Ogundehin.  Michelle has been our fantastic supporter over the years, including blog writing and supporting various campaigns we...

Read full story

16 June 2022

Royal celebration at Westminster Abbey

Breast Cancer UK joined hundreds of charities at a Service of Thanksgiving at Westminster Abbey to celebrate the remarkable difference they make in their communities.   His Royal Highness, The...

Read full story

13 June 2022

Parliamentary Event on Pesticides

In May our Head of Science, Margaret Wexler, spoke at a parliamentary event on pesticides. Organised by The Pesticide Collaboration and RSPB, and hosted by Luke Pollard, MP for Plymouth,...

Read full story

2 March 2022

Foxtrot Oscar Cancer (FOC)

Getting a cancer diagnosis understandably creates a whole jumble of emotions.  One is that you don’t want anyone else or their family to go through the same thing. And it's...

Read full story